A cBN-sintered-body tool produced by sintering fine cBN powder with various binders has excellent wear resistance and strength, and therefore exhibits excellent cutting performance for high-hardness iron-group metals and cast iron.
Here, the cBN sintered body is made up of cBN particles bound by a binder phase whose main components are TiN, TiC, W, Co, and Al. The cBN particles have a hardness and a heat conductivity that are second highest next to diamond, and have a superior fracture toughness to the ceramic material. The cBN sintered body having a high content of cBN particles is therefore excellent in characteristics such as plastic deformation resistance, toughness, strength, and chipping resistance.
As machine tools have become automated and production processes have become unattended in recent years, the chip treatability has become considered as an important factor indispensable for continuous running of the machine tools. In order to improve the chip treatability, generally a chip breaker is formed on a rake face of a tool, and a variety of methods are under study.
For example, Japanese Patent Laying-Open No. 3-178736 (PTL 1) discloses a method by which a rake face of a cutting tool is laser-machined or electrical discharge-machined to form a chip breaker. According to the method of PTL 1, after the chip breaker is formed, the tool is processed for the purpose of lessening damages caused in the process of forming the chip breaker, to thereby enable the cutting performance to be enhanced.
Further, Japanese Patent Laying-Open Nos. 2004-223648 (PTL 2) and 2006-281386 (PTL 3) each disclose a method by which a chip breaker is formed and thereafter its surface is processed with a loose abrasive. According to the method disclosed in PTL 2 and PTL 3, occurrence of adhesion due to surface roughness or altered structure appearing on the surface of the chip breaker is reduced, and machining damages such as internal cracks are removed. Accordingly, chipping is less likely to occur to the cutting tool.